Researchers reported at Barcelona on a study looking at the risk for heterosexual HIV-transmission to women through receptive anal sex between HIV-infected men and their monogomous female partners. They used data from the California Partners Study. 30% of the couples reported having both anal and vaginal intercourse. 62% of the HIV transmissions were believed to be due to anal contact. The researchers reported that the risk of transmission for each individual anal contact was 10 times higher than the risk for each individual vaginal contact. These authors concluded that the results confirm their previous finding that anal intercourse is a far more efficient mode of transmission than vaginal intercourse. They say further that a significant proportion of heterosexual HIV transmission results from anal sex particularly among people who practice anal sex a lot. The authors also suggest that since this is a large problem & is not receiving adequate attention, more attention needs to be paid to it with microbicide development, STD & AIDS prevention programs, and microbicide development. Gilead Sciences is developing a cream or gel for Tenofovir as a microbicide to prevent vaginal heterosexual transmission. They should also consider developing a cream for to prevent anal transmission for MSM & heterosexual contact.

The authors mentioned that in countries such as Brazil studies have reported up to 60% of adults practice anal sex, and it's estimated that in the USA about 7 times more women than men who have sex with men engage at least occasionally in unprotected receptive anal intercourse. The authors also say anal sex is relatively common in many regions of the world, and more frequently reported among people at high risk foe getting HIV: IVDUs, sex workers, adolescents. And they say that condom are not used as often for hetersexual anal sex compared to vaginal sex.